A woman hugs a firefighter before the start of a memorial service, Monday, July 1, 2013 in Prescott, Ariz.

PRESCOTT, Ariz. (AP) — Fire crews battling a wildfire should identify escape routes and safe zones. They should pay close attention to the weather forecast. And they should post lookouts.

The federal government issued those standards and others nearly two decades ago after a wildfire tragedy in Colorado. On Tuesday, investigators from around the U.S. arrived in Arizona to examine whether 19 crack firefighters who perished over the weekend heeded those rules or ignored them and paid with their lives.

In the nation's biggest loss of firefighters since 9/11, violent wind gusts Sunday turned what was believed to be a relatively manageable lightning-ignited forest fire in the town of Yarnell into a death trap that left no escape for a team of Hotshots.

The tragedy raised questions of whether the crew should have been pulled out much earlier and whether all the usual precautions would have made any difference at all in the face of triple-digit temperatures, erratic winds and tinderbox conditions that caused the fire to explode.

In 1994, 14 firefighters died on Colorado's Storm King Mountain, and investigators afterward found numerous errors in the way the blaze was fought. The U.S. Forest Service revised its firefighting policies.

"The reforms after Storm King were collectively intended to prevent that from happening again, which was mass entrapment of an entire Hotshot crew," said Lloyd Burton, professor of environmental law and policy at the University of Colorado.

"There are so many striking parallels between this tragedy and what happened on Storm King in 1994, it's almost haunting."

Those changes included policies that say no firefighters should be deployed unless they have a safe place to retreat. They must also be continuously informed of changing weather.

"If you don't have those things in place, it's not advisable to deploy a team in the first place, because you can't guarantee their safety," Burton said.

The Hotshot team from Prescott entered the smoky wilderness over the weekend with backpacks, chainsaws and other heavy gear to remove brush and trees and deprive the flames of fuel.

But the blaze grew from 200 acres to about 2,000 in a matter of hours as "the wind kicked up to 40 to 50 mph gusts and it blew east, south, west — every which way," said Prescott City Councilman Len Scamardo.

"What limited information we have was there was a gust of wind from the north that blew the fire back and trapped them," Scamardo said.

Dick Mangan, a retired U.S. Forest Service safety official and consultant, said it is too early to say if the crew or those managing the fire made mistakes.

"The fact that they're dead and that they had to deploy fire shelters tells us that something was seriously wrong," Mangan said. But then again, he said, they may have been doing everything right, and "this just might have been a weather anomaly that nobody saw coming that happened too quickly to respond to."

He said the crew members might have taken too many risks because they were on familiar ground and were trying to protect a community they knew well.

"When you've got especially structures and residences involved, and you've got local resources, there's a fair amount of social and political pressure, some of it self-generated by the firefighters, who want to do a good job," Mangan said. "They don't want to see a community burn down. They want to get in there."

A team of fire officials drawn from across the country by Atlanta NIMO, or National Incident Management Organization, arrived in the area Tuesday to find out exactly what went wrong.

They plan to make their way into the charred fire scene and issue a preliminary report in the coming days, said Mary Rasmussen, a spokeswoman for the Southwest Area Incident Management Team.

With the investigation just beginning, it's not clear what help water- or retardant-dropping aircraft could have provided for the doomed crew.

One contractor, Neptune Aviation Services, had three aerial tankers making drops on the fire earlier in the day. But at the time the firefighters died, the planes had been grounded because of treacherous conditions, said chief executive Ronald Hooper.

"It wasn't safe for them to be in the air at that time," Hooper said. There were "severe winds, erratic winds and thunderstorms in the area."

However, government dispatch logs show at least two other planes were flying over the fire at the time, one large tanker and one small one. There was also at least one firefighting helicopter in the air early Sunday afternoon.

On Tuesday, about 500 firefighters battled the mountain blaze, which had burned about 13 square miles. Yavapai County authorities said about 200 homes and other structures burned in Yarnell, and hundreds of people were evacuated.

Wind even more powerful than the gusts that hit Sunday were forecast for Tuesday and could reach 80 mph, said National Weather Service meteorologist Jim Wallmann.

No part of the fire had been contained, and thunderstorms that could bring little rain and lots of lightning remained a major threat, said Karen Takai, a spokeswoman for the firefighting effort.

Takai said the firefighters know how to stay focused on their task, even while battling their grief.